Technology Field
The present invention relates to a data writing method for a rewritable non-volatile memory module, and a memory controller and a memory storage apparatus using the method.
Description of Related Art
Along with the widespread of digital cameras, mobile phones, and MP3 in recent years, consumers' demand for storage media has increased drastically. Because a rewritable non-volatile memory has the characteristics of non-volatility of data, low power consumption, small volume, non-mechanical structure, and fast reading and writing speed, the rewritable non-volatile memory is the most adaptable memory to be applied in a portable electronic product, e.g. a notebook computer. A solid state drive (SSD) is a storage apparatus which utilizes a flash memory as its storage medium. Therefore, the flash memory industry has become a very popular part of the electronic industry in recent years.
As semiconductor manufacturing technology advances, a flash memory module with memory cells capable of storing multiple bits of data has been developed. Specifically, to write (or to program) data to the memory cell, a voltage applied to a certain terminal in the memory cell is controlled to change the electron volume in a charge-trapping layer in the gate, for example, so that the conduction state of the channel of the memory cell is changed to present a different storage state. Take a multi-level cell (MLC) NAND flash memory as an example, when the data of the lower page is 1, and the data of the upper page is 1 as well, the control circuit controls the word line control circuit not to change the gate voltage in the memory cell, so as to keep the storage state of the memory cell as “11”. When the data of the lower page is 1, and the data of the upper page is 0, the control circuit controls the word line control circuit to change the gate voltage in the memory cell, so as to change the storage state of the memory cell to “10”. When the data of the lower page is 0, and the data of the upper page is 0 as well, the control circuit controls the word line control circuit to change the gate voltage in the memory cell, so as to change the storage state of the memory cell to “00”. And, when the data of the lower page is 0, and the data of the upper page is 1, the control circuit controls the word line control circuit to change the gate voltage in the memory cell, so as to change the storage state of the memory cell to “01”. In other words, when reading data, the control circuit recognizes the storage state of the memory cell according to the current gate voltage of the memory cell.
However, when the flash memory module is in a high temperature environment, the data stored therein may be lost due to electric leakage of the memory cell. For instance, during mass production of the electronic products (e.g. mobile phones, tablet computers, and navigators) that are provided with embedded MMC (eMMC) chips, the eMMC chips with data (e.g. firmware codes) burnt thereon are mounted to the electronic devices through a high temperature solder furnace. At high temperature, however, the data in the eMMC chip may be lost, insulting in the malfunction of the electronic devices. In particular, if a physical block is not filled with data, the memory cell, which is yet programmed, on the word line has the highest potential. As a result, the adjacent memory cells with data stored therein suffer large electric leakage at the margin under high temperature, which causes data loss from the eMMC chip.
Therefore, how to prevent data stored in the flash memory module from being lost due to high temperature is one of the issues that need to be overcome in the industry.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.